Overview
- The peer-reviewed study by Orin Lole Durbin and colleagues was published on Oct. 2, 2026 in Science Advances and reexamined the fossil constraints used to date animal origins.
- Researchers analyzed more than 140 exceptionally preserved microfossils from the Kheseen Biota in Mongolia and found no specimens that can be confidently identified as animals, showing good preservation does not guarantee animal remains.
- The team argued that the absence of animals in Kheseen undermines using the Weng’an Ediacaran deposit as a firm 'maximum' age, because preservation or ecological factors can hide animals from the record.
- When molecular-clock analyses were run with older Tonian-age calibration points instead of Weng’an, estimates for the origin of crown-group animals shifted back about 200 million years to roughly 800–700 million years ago, though the authors stress this is not proof.
- An earlier origin would overlap Cryogenian glaciations and fit contested lipid-biomarker hints of pre-Ediacaran animals, so confirming the claim will require targeted field searches, new trace-fossil or biomarker evidence, and careful calibration of molecular clocks.